International Recommendations from An Expert Meeting
O ne of the recommendations from an expert meeting 1 regarding breast carcinoma treatment during pregnancy was that radiation therapy should be delayed until after delivery. However, we believe the authors have overestimated the risks of radiation therapy.
The risks of irradiation have been reviewed previously by the International Commission on Radiological Protection. 2,3 In general, the expected effects are malformations, a decrease in intelligence, mental retardation (deterministic effects), and cancer induction. For deterministic effects, threshold doses of 0.2 gray (Gy) have been found. An estimate of the lifetime risk of radiation-induced fatal cancer at 0.01 Gy is approximately 0.06%.
Maternal breast irradiation in the first 8 weeks of organogenesis will expose the fetus to 0.05-0.15 Gy (the reference dose is 50 Gy). Toward the end of pregnancy, the fetus lies closer to the radiation field and could receive >1 Gy for the same treatment course. 4 However, the fetal dose due to leakage radiation from the tube head of the linear accelerator and scatter from collimator and blocks can be reduced with a factor 2 to 4 by proper shielding.
Therefore, in the majority of cases, the radiation dose can be kept below the threshold dose for deterministic effects. The risk of radiation-induced cancer is low, and is negligible with a lifetime risk, without irradiation, of approximately 1 in 3.
A review of successful radiation therapy for breast cancer (as well as Hodgkin disease) with supplemental shielding during pregnancy was published recently. 5 In summary, the recommendation not to irradiate a pregnant patient until after birth is not tenable. Pregnancy is not a contraindication to radiotherapy in patients with breast cancer and other cancers that develop away from the pelvis.